This invention relates to devices for controllably dispensing a normally liquid, vaporizable substance to the atmosphere and, more particularly, to packages which encapsulate a liquid substance and are made from a material through which the liquid substance can permeate to the surrounding atmosphere.
Hermetically sealed envelopes or packages containing odorants, deodorants, insecticides, attractants, repellents and the like in concentrated liquid form and made from a flexible plastic material through which the liquid substance can permeate as a liquid and then vaporize into the surrounding atmosphere have been used to dispense such substances. Examples of envelopes or packages of this type are disclosed in the Watkins U.S. Pat. No. 3,785,556, issued Jan. 15, 1974 and the Watkins U.S. Pat. No. 3,885,737, issued May 27, 1975. Attention is also directed to the Poitras U.S. Pat. No. 3,343,664, issued Sept. 26, 1967.
To obtain a uniform dispensing rate of the liquid substance, it is desirable to maintain maximum surface contact between the interior surfaces of the package and the liquid substance throughout the effective life of the package. Prior art packages, such as those disclosed in the aboveidentified patents, usually include a single chamber for the liquid substance and the flexible walls of this chamber collapse under the influence of atmospheric pressure as the liquid substance is dispensed. If such a package is located in a nonhorizontal position during dispensing, the flexible walls of the package tend to be bagged or bulged outwardly by the liquid substance, permitting the liquid substance to accumulate in a lower portion. Consequently, it is possible for a substantial portion of the interior surfaces of the package to be out of contact with the liquid with a resultant reduction in the rate at which the liquid substance is dispensed.